Heretofore, when a shelf board is attached to a side board in assembling furniture or the like, there has been adopted a procedure wherein one edge of the shelf board is supported from thereunder by a supporting pin which is mounted on the side board beforehand. In this case, the shelf board is merely placed on the supporting pin and, therefore, is easily removed when the lower surface of the shelf board is pushed up. Therefore, when furniture is moved for rearrangement or relocation at home, the shelf board sometimes accidentally comes off and can result in injury or damage. Also, since the shelf board does not function as a strength member, the outer frame alone is unable to provide sufficient strength for a bookshelf, etc. and it tends to diagonally deform or otherwise the side board thereof is sometimes expanded sideward when goods are placed on the top board.
Therefore, there was developed a conventional assembling device 201 which, as shown in FIG. 7(a) and FIG. 7(b), is formed in a purse shape and includes an eccentric cam 202 formed on an inner surface thereof. The assembling device 201 is rotatably mounted to a shelf board 203. A head portion 206 of a screw 205 threadedly engaged with a side board 204 is inserted into an inserting opening 207 of the assembling device 201 so that the screw shank can project out through the slot between the axially opposed cam parts. Then, a driver (not shown) is inserted into a driver groove 208 and turned clockwise as shown in the figure. As a result, the screw 205 is drawn into the assembling device 201 as the device 201 moves toward the side board 204 by means of the function of the eccentric cam 202 in the manner as shown in FIG. 7(b). The head portion 206 is retained at or beyond an over-center change point X. The change point X basically represents the point on the concave surface of the cam 202 which must be rotated to the screw axis in order to achieve maximum engagement of the screw head 206 against the concave surface (see FIGS. 7(b) and 7(c). As a consequence, the shelf board 203 and the side board 204 are integrally formed.
In the conventional assembling device 201, however, when the shelf board 203 and the side board 204 are integrally formed, if the outwardly projecting length of the screw 205 is small, then the head portion 206 is retained before it reaches the over-center change point X. Therefore, when an external force is applied to the side board 204 in the direction as shown by arrow A in FIG. 7(c), the assembling device 201 is pulled by the head portion 206 of the screw 205 and turns counterclockwise in the figure. As a result, the connection between the side board 204 and the shelf board 203 is loosened. On the other hand, when the projecting length of the screw 205 is large, the side board 204 and the shelf board 203 cannot be integrally fixed with each other, since the head portion 206 never engages the cam 202. Therefore, when the side board 204 and the shelf board 203 are assembled together, the projecting length of the screw 205 must be accurately adjusted before-hand. Since it requires a number of initial adjustments to achieve the correct projecting length of the screw, working performance and production efficiency are difficult to obtain.
Therefore, the following construction is employed in the present invention in an attempt to solve the above-mentioned problems.